A new documentary centered on the life of late pop star Whitney Houston claims that the singer was molested as a child by her cousin.

For "Whitney," which premiered at the Cannes Film Festival Wednesday, Scottish filmmaker Kevin Macdonald said he pored over hours of private footage from Houston's archives. The Oscar-winning director said he interviewed members of her entourage and family who claim that Houston and her brother, Gary Houston, were molested by their cousin, Dee Dee Warwick. No charges were ever filed against Dee Dee Warwick.

Dee Dee Warwick, a Grammy-nominated artist who sang backup vocals for Wilson Pickett and Aretha Franklin, is the sister of Dionne Warwick. Dee Dee and Dionne were also nieces of Cissy Houston, Whitney's mother. Dee Dee Warwick was 18 years older than Whitney Houston and died in 2008.

When Cissy Houston, who also had a successful singing career singing backup for Franklin and Elvis Presley, went on tour, she would often leave her children with relatives, according to the documentary.

Gilles Petard/Redferns/Getty Images, FILE

In this undated file photo is a studio portrait of Dee Dee Warwick.

"I finally managed to persuade Mary Jones, who was Whitney’s longtime assistant and probably knew her in her last years more than anybody, to talk [on-camera]," Macdonald, 50, told Vanity Fair Wednesday about the molestation allegations presented in the film.

"She talks about what Whitney felt and what effect it had on her. So we changed the whole cut at the very last minute. It was kind of a detective story to get that piece of information, which changed how I felt about Whitney and how I felt about the story," the filmmaker continued.

In the documentary, Jones recounted a conversation she had with Houston before her death.

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She had tears in her eyes. She says, ‘Mommy don’t know the things we went through.’

"[The singer] looked at me and said, 'Mary, I was molested at a young age too. But it wasn’t by a man — it was a woman,'" recalled Jones. "She had tears in her eyes. She says, ‘Mommy don’t know the things we went through.’ I said, ‘Have you ever told your mother?’ She says, ‘No.’ I said, ‘Well, maybe you need to tell her.’ She said, ‘No, my mother would hurt somebody if I told her who it was.’ She just had tears rolling down her face, and I just hugged her. I said, ‘One day when you get the nerve, you need to tell your mother. It will lift the burden off you.'"

Also in "Whitney," out in theaters July 7, Houston's brother Gary revealed his own experience with molestation.

"Being a child — being seven, eight, nine years old — and being molested by a female family member of mine. My mother and father were gone a lot, so we stayed with a lot of different people ... four, five different families who took care of us," he said.

ABC Photo Archives/ABC via Getty Images, FILE

In this file photo, Whitney and Cissy Houston are featured on a special that celebrated moms and aired on Mother's Day, May 10,1987 on the ABC Television Network.

Macdonald told Vanity Fair that before he received confirmation of the allegations from family members, he had a suspicion that Houston had suffered abuse in some way.

"There was something very disturbed about her because she was never comfortable in her own skin," Macdonald told the magazine. "She seemed kind of asexual in a strange way. She was a beautiful woman, but she was never particularly sexy."

"I’ve seen and done some filming with people who have suffered childhood sexual abuse, and there was just something about her manner that was reminiscent to me of that sort of shrinking — a lack of comfort in her own physicality that felt -- maybe that is what it was," he added. "It took awhile for anyone to go on record about it, and eventually the family did."

Representatives for Dionne Warwick and Cissy Houston did not immediately return ABC News' request for comment. A rep for Gary Houston had no comment.

Houston died suddenly in 2012 at age 48. She became a mega pop star thanks to hits "I Wanna Dance with Somebody" and "I'm Every Woman," along with her 1992 blockbuster film, "The Bodyguard," where she starred opposite Kevin Costner and sang on its soundtrack.